Elastic wave device

Abstract

The present application reduces unwanted waves. An elastic wave device includes a support substrate, a piezoelectric layer 2 having two main surfaces in a first direction that is a thickness direction of the support substrate, containing lithium niobate or lithium tantalate, an energy confinement layer provided between the support substrate and the piezoelectric layer 2, and a first IDT electrode formed on one of the two main surfaces of the piezoelectric layer 2 and containing a first bus bar, a second bus bar, a plurality of first electrode fingers, and a plurality of second electrode fingers. At least a portion of the first IDT electrode is disposed in an area that overlaps the energy confinement layer in a view in the first direction. The thickness of the piezoelectric layer 2 is d, and the center-to-center distance between adjacent electrode fingers is p. In this case, d / p is 0.5 or less. The plurality of electrode fingers are arranged to have overlapping regions that overlap each other as viewed from the arrangement direction of the plurality of electrode fingers. In the overlapping regions, a gap is provided between at least a portion of at least one electrode finger and the piezoelectric layer 2.

Description

Technical Field

[0001] This disclosure relates to elastic wave devices. Background Technology

[0002] Patent document 1 describes an elastic wave device.

[0003] Prior art literature

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2012-257019 Summary of the Invention

[0006] The problem the invention aims to solve

[0007] In the elastic wave device of Patent Document 1, unwanted waves are generated both inside and outside the band, which may degrade the resonance characteristics. Therefore, it is necessary to reduce unwanted waves.

[0008] This disclosure is intended to address the aforementioned issues, with the aim of reducing unwanted waves.

[0009] Technical solutions for solving the problem

[0010] One type of elastic wave device includes: a support substrate; a piezoelectric layer having two main surfaces in a first direction, which is the thickness direction of the support substrate, comprising lithium niobate or lithium tantalate; an energy blocking layer disposed between the support substrate and the piezoelectric layer in the first direction; and a first IDT electrode formed on one of the two main surfaces of the piezoelectric layer, and including a first busbar, a second busbar, a plurality of first electrode fingers with base ends connected to the first busbar, and a plurality of second electrode fingers with base ends connected to the second busbar, wherein at least a portion of the first IDT electrode is disposed in the thickness direction of the support substrate. In a top-down view, the region at least partially overlaps with the energy sealing layer. The thickness of the piezoelectric layer is set as d, and the center-to-center distance between adjacent electrode fingers among the plurality of first electrode fingers and the plurality of second electrode fingers is set as p. In this case, d / p is less than 0.5. The plurality of first electrode fingers and the plurality of second electrode fingers are configured to have overlapping cross regions when viewed from the arrangement direction of the plurality of first electrode fingers and the plurality of second electrode fingers. In the cross regions, a first gap is provided between at least a portion of at least one of the plurality of first electrode fingers and the plurality of second electrode fingers and the piezoelectric layer.

[0011] Invention Effects

[0012] According to this disclosure, unwanted waves can be reduced. Attached Figure Description

[0013] Figure 1A This is a perspective view showing the elastic wave device of the first embodiment.

[0014] Figure 1B This is a top view showing the electrode structure of the first embodiment.

[0015] Figure 2 It is along Figure 1A A sectional view of the portion along line II-II.

[0016] Figure 3A This is a schematic cross-sectional view used to illustrate the Ram wave propagating in the piezoelectric layer of the comparative example.

[0017] Figure 3B This is a schematic cross-sectional view used to illustrate the bulk wave of the thickness shear first mode propagating in the piezoelectric layer of the first embodiment.

[0018] Figure 4 This is a schematic cross-sectional view used to illustrate the amplitude direction of the bulk wave of the thickness shear first mode propagating in the piezoelectric layer of the first embodiment.

[0019] Figure 5 This is an explanatory diagram showing an example of the resonant characteristics of the elastic wave device according to the first embodiment.

[0020] Figure 6 This is an explanatory diagram showing the relationship between d / 2p and the relative bandwidth of the resonator when the center-to-center distance or the average center-to-center distance of adjacent electrodes is set as p and the average thickness of the piezoelectric layer is set as d in the elastic wave device of the first embodiment.

[0021] Figure 7 This is a top view showing an example of an elastic wave device in the first embodiment having a pair of electrodes.

[0022] Figure 8 This is a reference diagram showing an example of the resonant characteristics of the elastic wave device according to the first embodiment.

[0023] Figure 9 This is an explanatory diagram showing the relationship between the relative bandwidth and the phase rotation amount of the spurious impedance, which is normalized by 180 degrees, when the elastic wave device of the first embodiment is composed of a plurality of elastic wave resonators.

[0024] Figure 10 This is an explanatory diagram showing the relationship between d / 2p, metallization ratio (MR), and relative bandwidth.

[0025] Figure 11 This is an illustrative diagram showing the mapping of the relative bandwidth to the Euler angles (0°, θ, ψ) of LiNbO3 when d / p is infinitely close to 0.

[0026] Figure 12 This is a variation of the first embodiment, and is along... Figure 1A A sectional view of the portion along line II-II.

[0027] Figure 13 This is a partially cut perspective view used to illustrate the elastic wave device involved in the embodiments of this disclosure.

[0028] Figure 14 This is a top view showing an embodiment of the elastic wave device according to the first embodiment.

[0029] Figure 15 It is along Figure 14 An example of a cross-sectional view of the EE′ line.

[0030] Figure 16 It is along Figure 14 An example of a cross-sectional view of the FF' line.

[0031] Figure 17A This is a first explanatory diagram showing the resonant characteristics of the elastic wave device according to the first embodiment.

[0032] Figure 17B This is a second explanatory diagram showing the resonant characteristics of the elastic wave device according to the first embodiment.

[0033] Figure 17C This is the third explanatory diagram showing the resonant characteristics of the elastic wave device according to the first embodiment.

[0034] Figure 18 It is along Figure 14 The first variation of the sectional view of the EE′ line.

[0035] Figure 19 It is along Figure 14 The second variation of the sectional view of the EE′ line.

[0036] Figure 20 It is along Figure 14 The third variation of the sectional view of the EE′ line.

[0037] Figure 21 It is along Figure 14 The fourth variation of the sectional view of the FF′ line.

[0038] Figure 22 It is along Figure 14 The fifth variation of the sectional view of the FF′ line.

[0039] Figure 23 This is a top view showing an embodiment of the elastic wave device according to the second embodiment.

[0040] Figure 24 It is along Figure 23 An example of a cross-sectional view of the GG' line.

[0041] Figure 25 It is along Figure 23 An example of a cross-sectional view of the HH′ line.

[0042] Figure 26 This is a first explanatory diagram showing the resonant characteristics of the elastic wave device according to the second embodiment.

[0043] Figure 27 This is a second explanatory diagram showing the resonant characteristics of the elastic wave device according to the second embodiment. Detailed Implementation

[0044] Hereinafter, embodiments of the present disclosure will be described in detail based on the accompanying drawings. However, the present disclosure is not limited to these embodiments. Furthermore, the embodiments described in this disclosure are exemplary, and partial substitutions or combinations of structures can be made between different embodiments. From the modified examples and the second embodiment onwards, descriptions of matters common to the first embodiment are omitted, and only the differences are described. In particular, the same effects based on the same structure will not be mentioned repeatedly in each embodiment.

[0045] (First Embodiment)

[0046] Figure 1A This is a perspective view showing the elastic wave device of the first embodiment. Figure 1B This is a top view showing the electrode structure of the first embodiment.

[0047] The elastic wave device 1 of the first embodiment has a piezoelectric layer 2 comprising LiNbO3. The piezoelectric layer 2 may also comprise LiTaO3. In the first embodiment, the cutting angle of LiNbO3 and LiTaO3 is Z-cut. The cutting angle of LiNbO3 and LiTaO3 may also be rotational Y-cut or X-cut. Preferably, the propagation orientation is ±30° of Y propagation and X propagation.

[0048] The thickness of the piezoelectric layer 2 is not particularly limited, but in order to effectively excite the first-order mode of thickness shearing, it is preferably 50 nm or more and 1000 nm or less.

[0049] The piezoelectric layer 2 has a first main surface 2a and a second main surface 2b that are opposite to each other in the Z direction. Electrode fingers 3 and 4 are provided on the first main surface 2a.

[0050] Here, electrode finger 3 is an example of "first electrode finger," and electrode finger 4 is an example of "second electrode finger." Figure 1A as well as Figure 1BIn this configuration, multiple electrode fingers 3 are connected to the first bus bar 5. Multiple electrode fingers 4 are connected to the second bus bar 6. The multiple electrode fingers 3 and multiple electrode fingers 4 are interleaved with each other. Thus, an IDT electrode is formed, comprising electrode fingers 3, electrode fingers 4, the first bus bar 5, and the second bus bar 6.

[0051] Electrode fingers 3 and 4 have a rectangular shape and a length direction. Electrode finger 3 and its adjacent electrode finger 4 are positioned opposite each other in a direction orthogonal to this length direction. The length directions of electrode fingers 3 and 4, as well as the directions orthogonal to their length directions, are all directions intersecting the thickness direction of the piezoelectric layer 2. Therefore, it can also be said that electrode finger 3 and its adjacent electrode finger 4 are opposite each other in a direction intersecting the thickness direction of the piezoelectric layer 2. In the following description, the thickness direction of the piezoelectric layer 2 is sometimes defined as the Z direction (or the first direction), the length directions of electrode fingers 3 and 4 as the Y direction (or the second direction), and the direction orthogonal to electrode fingers 3 and 4 as the X direction (or the third direction).

[0052] Furthermore, the length directions of electrode fingers 3 and 4 can also be aligned with... Figure 1A as well as Figure 1B The directions shown are reversed, being perpendicular to the length directions of electrode fingers 3 and 4. That is, in Figure 1A as well as Figure 1B Alternatively, electrode fingers 3 and 4 can extend in the direction in which the first busbar 5 and the second busbar 6 extend. In this case, the first busbar 5 and the second busbar 6... Figure 1A as well as Figure 1B The electrode fingers 3 and 4 extend in the same direction. Furthermore, multiple pairs of adjacent electrode fingers 3 connected to one potential and electrode fingers 4 connected to another potential are provided in a direction orthogonal to the length direction of the electrode fingers 3 and 4.

[0053] Here, "adjacent to electrode fingers 3 and 4" does not mean that electrode fingers 3 and 4 are configured in direct contact, but rather that they are configured with a gap between them. Furthermore, when electrode fingers 3 and 4 are adjacent, no electrodes connected to the signal (hot) electrode or ground electrode, including other electrode fingers 3 and 4, are placed between electrode fingers 3 and 4. This pairing does not need to be an integer number of pairs; it can be 1.5 pairs, 2.5 pairs, etc.

[0054] The center-to-center distance between electrode fingers 3 and 4 is preferably in the range of 1 μm or more and 10 μm or less. Furthermore, the center-to-center distance between electrode fingers 3 and 4 is defined as the distance connecting the center of the width dimension of electrode finger 3 in a direction orthogonal to the length direction of electrode finger 3 and the center of the width dimension of electrode finger 4 in a direction orthogonal to the length direction of electrode finger 4.

[0055] Furthermore, when there are multiple electrode fingers 3 and 4 (in the case where there are 1.5 or more electrode groups if electrode fingers 3 and 4 are considered as a pair of electrode groups), the center-to-center distance of electrode fingers 3 and 4 refers to the average center-to-center distance of adjacent electrode fingers 3 and 4 in 1.5 or more pairs of electrode fingers 3 and 4.

[0056] Furthermore, the width of electrode fingers 3 and 4, that is, the dimensions of electrode fingers 3 and 4 in the opposing direction, is not particularly limited, but is preferably in the range of 150 nm or more and 1000 nm or less. Additionally, the center-to-center distance between electrode fingers 3 and 4 is the distance connecting the center of the dimension (width dimension) of electrode finger 3 in a direction orthogonal to the length direction of electrode finger 3 and the center of the dimension (width dimension) of electrode finger 4 in a direction orthogonal to the length direction of electrode finger 4.

[0057] Furthermore, in the first embodiment, a Z-cut piezoelectric layer is used, so the direction orthogonal to the length direction of electrode fingers 3 and 4 becomes the direction orthogonal to the polarization direction of piezoelectric layer 2. This is not a limitation if a piezoelectric material with other cut angles is used as piezoelectric layer 2. Here, "orthogonal" is not limited to strictly orthogonal; it can also be approximately orthogonal (the angle between the direction orthogonal to the length direction of electrode fingers 3 and 4 and the polarization direction is, for example, 90° ± 10°).

[0058] A support substrate 8 is stacked on the second main surface 2b of the piezoelectric layer 2, separated by a dielectric film 7. The dielectric film 7 and the support substrate 8 have a frame-like shape, and as shown... Figure 2 As shown, it has openings 7a and 8a. As a result, a cavity (air gap) 9 is formed.

[0059] The void 9 is provided so as not to interfere with the vibration of the excitation region C of the piezoelectric layer 2. Therefore, the support substrate 8 is laminated on the second main surface 2b with the dielectric film 7 in a position that does not overlap with the portion where at least one pair of electrode fingers 3 and electrode fingers 4 are provided. Alternatively, the dielectric film 7 may not be provided. Therefore, the support substrate 8 may be laminated directly or indirectly on the second main surface 2b of the piezoelectric layer 2.

[0060] The dielectric film 7 is formed of silicon oxide. However, in addition to silicon oxide, the dielectric film 7 can also be formed of suitable insulating materials such as silicon nitride and bauxite.

[0061] The support substrate 8 is formed of Si. The orientation of the surface on the piezoelectric layer 2 side of Si can be (100), (110), or (111). Preferably, it is Si with a high resistivity of 4kΩ or higher. However, the support substrate 8 can also be constructed using suitable insulating materials or semiconductor materials. For example, piezoelectric materials such as alumina, lithium tantalate, lithium niobate, and quartz, bauxite, magnesium oxide, sapphire, silicon nitride, aluminum nitride, silicon carbide, zirconium oxide, cordierite, mullite, block talc, and forsterite, as well as various ceramics, diamond, glass, and other dielectrics, and gallium nitride and other semiconductors can be used as materials for the support substrate 8.

[0062] The aforementioned plurality of electrode fingers 3, 4, and the first busbar 5 and second busbar 6 comprise suitable metals or alloys such as Al or AlCu alloys. In the first embodiment, the electrode fingers 3, 4, 5, and 6 have a structure in which an Al film is laminated on a Ti film. Alternatively, a close-fitting layer other than a Ti film may also be used.

[0063] During driving, an AC voltage is applied between multiple electrode fingers 3 and multiple electrode fingers 4. More specifically, an AC voltage is applied between the first bus bar 5 and the second bus bar 6. As a result, the resonant characteristics of a bulk wave utilizing the thickness shear first-order mode excited in the piezoelectric layer 2 can be obtained.

[0064] Furthermore, in the elastic wave device 1, the thickness of the piezoelectric layer 2 is set as d, and the center-to-center distance between any two adjacent pairs of electrode fingers 3 and 4 is set as p. In this case, d / p is set to 0.5 or less. Therefore, a bulk wave with the aforementioned thickness shear first mode can be effectively excited, and good resonance characteristics can be obtained. More preferably, d / p is 0.24 or less, in which case even better resonance characteristics can be obtained.

[0065] Furthermore, in the case where at least one of the electrode fingers 3 and electrode fingers 4 exists in multiples, as in the first embodiment, that is, when there are 1.5 or more pairs of electrode fingers 3 and electrode fingers 4 if the electrode fingers 3 and electrode fingers 4 are set as a pair of electrode groups, the center-to-center distance p of adjacent electrode fingers 3 and electrode fingers 4 becomes the average distance between the center-to-center distances of each adjacent electrode finger 3 and electrode finger 4.

[0066] In the elastic wave device 1 of the first embodiment, the above-described structure is provided, so even if the number of pairs of electrode fingers 3 and 4 is reduced in order to achieve miniaturization, a decrease in the Q value is not easily generated. This is because it is a resonator that does not require reflectors on both sides, resulting in low propagation loss. Furthermore, the reason why the above-described reflectors are not required is due to the use of a thickness-sheared first-order mode bulk wave.

[0067] Figure 3A This is a schematic cross-sectional view used to illustrate the Ram wave propagating in the piezoelectric layer of the comparative example. Figure 3B This is a schematic cross-sectional view used to illustrate the bulk wave of the thickness shear first mode propagating in the piezoelectric layer of the first embodiment. Figure 4 This is a schematic cross-sectional view used to illustrate the amplitude direction of the bulk wave of the thickness shear first mode propagating in the piezoelectric layer of the first embodiment.

[0068] exist Figure 3A In this case, it is an elastic wave device as described in Patent Document 1, where the Lamb wave propagates in the piezoelectric layer. For example... Figure 3A As shown, the wave propagates in the piezoelectric layer 201 as indicated by the arrow. Here, in the piezoelectric layer 201, there are a first main surface 201a and a second main surface 201b, and the thickness direction connecting the first main surface 201a and the second main surface 201b is the Z direction. The X direction is the direction in which the electrode fingers 3 and 4 of the IDT electrodes are arranged. Figure 3A As shown, if it is a Lamb wave, the wave propagates in the X direction, as illustrated. Because it is a plate wave, although the piezoelectric layer 201 vibrates as a whole, the wave propagates in the X direction, thus resonant characteristics are obtained by placing reflectors on both sides. Therefore, wave propagation loss occurs, and the Q value decreases in the pursuit of miniaturization, i.e., by reducing the logarithm of electrode fingers 3 and 4.

[0069] In contrast, such as Figure 3B As shown, in the elastic wave device of the first embodiment, the vibration displacement is in the thickness shear direction. Therefore, the wave propagates and resonates substantially in the direction connecting the first principal surface 2a and the second principal surface 2b of the piezoelectric layer 2, i.e., in the Z direction. That is, the X-direction component is significantly smaller than the Z-direction component of the wave. Moreover, since the resonance characteristic is obtained through the propagation of the wave in this Z-direction, a reflector is not required. Therefore, no propagation loss occurs during reflector propagation. Thus, even if the number of electrode pairs including electrode fingers 3 and electrode fingers 4 is reduced for the purpose of miniaturization, a decrease in the Q value is not easily generated.

[0070] In addition, such as Figure 4 As shown, the amplitude direction of the bulk wave of the first-order thickness shear mode is in the excitation region C of the piezoelectric layer 2 (reference). Figure 1B The first region 451 contained in region C and the second region 452 contained in region C become opposite. Figure 4 The diagram schematically illustrates a body wave when a voltage higher than that of electrode finger 4 is applied between electrode finger 3 and electrode finger 4. The first region 451 is the region between the imaginary plane VP1 and the first main surface 2a in the excitation region C. This imaginary plane VP1 is orthogonal to the thickness direction of the piezoelectric layer 2 and divides the piezoelectric layer 2 into two parts. The second region 452 is the region between the imaginary plane VP1 and the second main surface 2b in the excitation region C.

[0071] In the elastic wave device 1, at least one pair of electrodes, including electrode fingers 3 and electrode fingers 4, is provided. However, since the wave is not propagated in the X direction, the number of electrode pairs including electrode fingers 3 and electrode fingers 4 does not necessarily have to be multiple. That is, it is sufficient to provide at least one pair of electrodes.

[0072] For example, electrode 3 is an electrode connected to the signal potential, and electrode 4 is an electrode connected to the ground potential. However, it is also possible that electrode 3 is connected to the ground potential, and electrode 4 is connected to the signal potential. In the first embodiment, as described above, at least one pair of electrodes is either an electrode connected to the signal potential or an electrode connected to the ground potential, and no floating electrode is provided.

[0073] Figure 5 This is an explanatory diagram showing an example of the resonant characteristics of the elastic wave device according to the first embodiment. Additionally, we obtain... Figure 5 The design parameters of the elastic wave device 1 with the resonant characteristics shown are as follows.

[0074] Piezoelectric layer 2: LiNbO3 with Euler angles of (0°, 0°, 90°)

[0075] Thickness of piezoelectric layer 2: 400nm

[0076] Excitation region C (reference) Figure 1B Length: 40μm

[0077] Number of electrode pairs including electrode fingers 3 and 4: 21 pairs

[0078] Center-to-center distance (split) between electrode finger 3 and electrode finger 4: 3 μm

[0079] Width of electrode finger 3 and electrode finger 4: 500nm

[0080] d / p: 0.133

[0081] Dielectric film 7: Silicon oxide film with a thickness of 1 μm

[0082] Support substrate 8: Si

[0083] In addition, the so-called incentive region C (refer to) Figure 1BThe excitation region C is the area where electrode fingers 3 and 4 overlap when viewed in the X direction, which is orthogonal to the length direction (Y direction) of electrode fingers 3 and 4. Here, the so-called excitation region C is an example of an "intersection region". The length of the excitation region C is its dimension along the length direction of electrode fingers 3 and 4.

[0084] In the first embodiment, the distance between the electrodes of the electrode pairs including electrode fingers 3 and electrode fingers 4 is set to be equal in all pairs. That is, electrode fingers 3 and electrode fingers 4 are arranged at equal intervals.

[0085] according to Figure 5 It is clear that, despite the absence of a reflector, a good resonant characteristic with a relative bandwidth of 12.5% ​​was still achieved.

[0086] Furthermore, if the thickness of the piezoelectric layer 2 is set as d, and the center-to-center distance between the electrodes of electrode finger 3 and electrode finger 4 is set as p, then in the first embodiment, d / p is 0.5 or less, more preferably 0.24 or less. (Refer to...) Figure 6 This needs to be explained.

[0087] With Get Figure 5 Similarly, the elastic wave device with the resonant characteristics shown is obtained by changing d / 2p, thus obtaining multiple elastic wave devices. Figure 6 This is an explanatory diagram showing the relationship between d / 2p and the relative bandwidth of the resonator when the center-to-center distance or the average center-to-center distance of adjacent electrodes is set as p and the average thickness of the piezoelectric layer 2 is set as d in the elastic wave device of the first embodiment.

[0088] like Figure 6 As shown, if d / 2p exceeds 0.25, i.e., if d / p > 0.5, then even if d / p is adjusted, the relative bandwidth is less than 5%. In contrast, when d / 2p ≤ 0.25, i.e., when d / p ≤ 0.5, if d / p is varied within this range, the relative bandwidth can be increased to 5% or more, i.e., a resonator with a high coupling coefficient can be constructed. Furthermore, when d / 2p is 0.12 or less, i.e., when d / p is 0.24 or less, the relative bandwidth can be increased to 7% or more. In addition, if d / p is adjusted within this range, a resonator with a wider relative bandwidth can be obtained, and a resonator with a higher coupling coefficient can be achieved. Therefore, it can be seen that by setting d / p to 0.5 or less as in the second invention of this application, a resonator with a high coupling coefficient utilizing the aforementioned thickness shear first-order mode of the bulk wave can be constructed.

[0089] Alternatively, at least one pair of electrodes can be used. In the case of one pair of electrodes, p is defined as the distance between the centers of adjacent electrode fingers 3 and 4. Furthermore, in the case of 1.5 or more pairs of electrodes, p can simply be the average distance between the centers of adjacent electrode fingers 3 and 4.

[0090] Furthermore, regarding the thickness d of the piezoelectric layer 2, even if the piezoelectric layer 2 has a thickness deviation, it is sufficient to use a value that has been averaged over its thickness.

[0091] Figure 7 This is a top view showing an example of an elastic wave device according to the first embodiment, in which a pair of electrodes are provided. In the elastic wave device 101, a pair of electrodes having electrode fingers 3 and electrode fingers 4 are provided on the first main surface 2a of the piezoelectric layer 2. Furthermore, Figure 7 K in the figure represents the cross width. As previously mentioned, in the elastic wave device of this disclosure, the number of electrode pairs can also be one. Even in this case, as long as the above d / p is less than or equal to 0.5, a first-order thickness shear mode of a bulk wave can be effectively excited.

[0092] In the elastic wave device 1, preferably, among the plurality of electrode fingers 3 and 4, the metallization ratio MR of any adjacent electrode fingers 3 and 4 relative to the excitation region C preferably satisfies MR ≤ 1.75(d / p) + 0.075, where the excitation region C is the region where the aforementioned adjacent electrode fingers 3 and 4 overlap when viewed in opposite directions. In this case, stray emissions can be effectively reduced. (Refer to...) Figure 8 as well as Figure 9 This needs to be explained.

[0093] Figure 8 This is a reference diagram showing an example of the resonant characteristics of the elastic wave device according to the first embodiment. Strays, as indicated by arrow B, appear between the resonant frequency and the anti-resonant frequency. Furthermore, d / p is set to 0.08, and the Euler angles of LiNbO3 are set to (0°, 0°, 90°). Additionally, the aforementioned metallization ratio is set to MR = 0.35.

[0094] Reference Figure 1B The metallization ratio (MR) is explained. Figure 1BIn the electrode structure, considering only a pair of electrode fingers 3 and 4, it is assumed that only this pair of electrode fingers 3 and 4 are provided. In this case, the portion enclosed by the single-dotted line is called the excitation region C. This excitation region C refers to the area where electrode fingers 3 overlaps with electrode finger 4, the area where electrode finger 4 overlaps with electrode finger 3, and the area where electrode fingers 3 and 4 overlap when observed in a direction orthogonal to the length direction of electrode fingers 3 and 4 (i.e., the opposing direction), as well as the area between electrode fingers 3 and 4. Furthermore, the ratio of the area of ​​electrode fingers 3 and 4 within the excitation region C to the area of ​​the excitation region C is called the metallization ratio MR. That is, the metallization ratio MR is the ratio of the area of ​​the metallized portion to the area of ​​the excitation region C.

[0095] In addition, when multiple pairs of electrode fingers 3 and 4 are provided, the ratio of the total area of ​​the metallized portion contained in the entire excitation region C to the total area of ​​the excitation region C can be used as MR.

[0096] Figure 9 This is an explanatory diagram showing the relationship between the relative bandwidth and the phase rotation amount of the stray impedance, which is normalized by 180 degrees, when the elastic wave device of the first embodiment is composed of a plurality of elastic wave resonators. Furthermore, various changes and adjustments were made to the film thickness of the piezoelectric layer 2 and the dimensions of the electrode fingers 3 and 4 regarding the relative bandwidth. In addition, Figure 9 This is the result when using piezoelectric layer 2 with Z-cut LiNbO3, but the same tendency occurs even when using piezoelectric layer 2 with other cut angles.

[0097] exist Figure 9 In the region enclosed by ellipse J, the stray energy increases to 1.0. According to... Figure 9 It is clear that if the relative bandwidth exceeds 0.17, that is, if the relative bandwidth exceeds 17%, then even if the parameters constituting the relative bandwidth are changed, large spurious signals with a spurious level greater than 1 will appear in the passband. That is, like... Figure 8 As shown in the resonance characteristics, large stray rays appear within the band, as indicated by arrow B. Therefore, the relative bandwidth is preferably 17% or less. In this case, the stray rays can be reduced by adjusting the thickness of the piezoelectric layer 2, the dimensions of the electrode fingers 3 and 4, etc.

[0098] Figure 10 This is an explanatory diagram showing the relationship between d / 2p, metallization ratio MR, and relative bandwidth. In the elastic wave device 1 of the first embodiment, various elastic wave devices 1 with different d / 2p and MR were constructed, and the relative bandwidth was measured. Figure 10The area to the right of the dashed line D, indicated by the shading, represents a region with a relative bandwidth of 17% or less. The boundary between this shaded and unshaded region can be represented by MR = 3.5(d / 2p) + 0.075, or MR = 1.75(d / p) + 0.075. Therefore, it is preferable that MR ≤ 1.75(d / p) + 0.075. In this case, it is easier to achieve a relative bandwidth of 17% or less. More preferably... Figure 10 The region to the right of the dashed line D1 in the diagram is MR = 3.5(d / 2p) + 0.05. That is, as long as MR ≤ 1.75(d / p) + 0.05, the relative bandwidth can be reliably kept below 17%.

[0099] Figure 11 This is an illustrative diagram showing the mapping of the relative bandwidth to the Euler angles (0°, θ, ψ) of LiNbO3 when d / p is infinitely close to 0. Figure 11 The area shown by the shading is the region where a relative bandwidth of at least 5% can be obtained. If the range of the region is approximated, it becomes the range represented by the following equations (1), (2) and (3).

[0100] (0°±10°, 0°~20°, any ψ) …Equation (1)

[0101] (0°±10°, 20°~80°, 0°~60°(1-(θ-50) 2 / 900) 1 / 2 () or (0°±10°, 20°~80°, [180°-60°(1-(θ-50))) 2 / 900) 1 / 2 [~180°) …Equation (2)

[0102] (0°±10°,[180°-30°(1-(ψ-90) 2 / 8100) 1 / 2 ~180°, any ψ)

[0103] …Formula (3)

[0104] Therefore, within the range of Euler angles in equations (1), (2), or (3) above, it is preferable to be able to sufficiently widen the relative bandwidth.

[0105] Figure 12 This is a variation of the first embodiment, and is along... Figure 1AA cross-sectional view of line II-II. In the elastic wave device 41, an acoustic multilayer film 42 is stacked on the second main surface 2b of the piezoelectric layer 2. The acoustic multilayer film 42 has a stacked structure of low acoustic impedance layers 42a, 42c, and 42e with relatively low acoustic impedance and high acoustic impedance layers 42b and 42d with relatively high acoustic impedance. When the acoustic multilayer film 42 is used, even without using the void portion 9 in the elastic wave device 1, the bulk wave of the thickness shear first mode can be contained within the piezoelectric layer 2. In the elastic wave device 41, by setting the above-mentioned d / p to 0.5 or less, the resonance characteristics of the bulk wave based on the thickness shear first mode can also be obtained. In addition, the number of stacked layers of the low acoustic impedance layers 42a, 42c, 42e and the high acoustic impedance layers 42b and 42d in the acoustic multilayer film 42 is not particularly limited. It is sufficient that at least one high acoustic impedance layer 42b, 42d is disposed on the side further away from the piezoelectric layer 2 than the low acoustic impedance layers 42a, 42c, 42e.

[0106] As long as the aforementioned acoustic impedance relationship is satisfied, the low acoustic impedance layers 42a, 42c, and 42e, and the high acoustic impedance layers 42b and 42d can be made of suitable materials. For example, silicon oxide or silicon oxynitride can be used as materials for the low acoustic impedance layers 42a, 42c, and 42e. Furthermore, bauxite, silicon nitride, or metals can be used as materials for the high acoustic impedance layers 42b and 42d.

[0107] Figure 13 This is a partially cut-out perspective view used to illustrate the elastic wave device according to embodiments of this disclosure. Figure 13 In the diagram, the outer periphery of the cavity 9 is shown by a dashed line. The elastic wave device of this disclosure can also utilize plate waves. In this case, such as... Figure 13 As shown, the elastic wave device 301 includes reflectors 310 and 311. Reflectors 310 and 311 are disposed on both sides of the electrode fingers 3 and 4 of the piezoelectric layer 2 in the direction of elastic wave propagation. In the elastic wave device 301, by applying an alternating electric field to the electrode fingers 3 and 4 on the cavity portion 9, a Lamb wave, which is a plate wave, can be excited. At this time, because reflectors 310 and 311 are disposed on both sides, resonance characteristics based on the Lamb wave as a plate wave can be obtained.

[0108] As explained above, in elastic wave devices 1 and 101, a thickness-shearing first-order mode bulk wave is utilized. Furthermore, in elastic wave devices 1 and 101, the first electrode finger 3 and the second electrode finger 4 are adjacent electrodes. The thickness of the piezoelectric layer 2 is set as d, and the center-to-center distance between the first electrode finger 3 and the second electrode finger 4 is set as p. In this case, d / p is set to 0.5 or less. Therefore, even with miniaturization of the elastic wave device, the Q value can be improved.

[0109] In the elastic wave devices 1 and 101, the piezoelectric layer 2 is formed of lithium niobate or lithium tantalate. Preferably, the first main surface 2a or the second main surface 2b of the piezoelectric layer 2 has a first electrode finger 3 and a second electrode finger 4 facing each other in a direction intersecting the thickness direction of the piezoelectric layer 2, and the first electrode finger 3 and the second electrode finger 4 are covered with a protective film.

[0110] In the elastic wave devices 1 and 41, an energy-sealing layer is provided between the piezoelectric layer 2 and the support substrate 8. The energy-sealing layer is a layer used to contain elastic waves, such as bulk waves with a first-order shear mode, within the piezoelectric layer 2. Examples of energy-sealing layers include the void portion 9 and the acoustic multilayer film 42.

[0111] Figure 14 This is a top view illustrating an embodiment of the elastic wave device according to the first embodiment. Figure 14 As shown, the elastic wave device 1A according to the first embodiment has a first IDT electrode 30 on the first main surface 2a of the piezoelectric layer 2. The first IDT electrode 30 includes a first bus bar 5, a second bus bar 6, a first electrode finger 3, and a second electrode finger 4.

[0112] Figure 15 It is along Figure 14 An example of a cross-sectional view of the EE′ line. For example... Figure 15 As shown, a first gap 10 is provided between electrode fingers 3 and 4 and the piezoelectric layer 2. The first gap 10 is a gap provided between the first electrode finger 3 or the second electrode finger 4 and the first main surface 2a of the piezoelectric layer 2. Figure 15 In the example, the first gap 10 opens upwards in both the X and Y directions on the side where the electrode fingers 3 and 4 are not connected to the busbars 5 and 6. Here, the height of the first gap 10, that is, the length of the first gap 10 in the Z direction, is defined as hv1. In this case, hv1 is preferably 0.1 nm or more and 100 nm or less, more preferably 1 nm or more and 20 nm or less. Furthermore, if the height of the first gap 10 has a deviation, an averaged value of that height can be used as hv1.

[0113] Figure 16 It is along Figure 14 An example of a cross-sectional view of the FF' line. For example... Figure 16As shown, viewed from above in the Z direction, at least a portion of the electrode fingers 3 and 4 are disposed in the region overlapping with the energy sealing layer such as the void portion 9. Here, the sum of the heights of the electrode fingers 3 and 4, i.e., the height of the first void 10 and the thickness (length in the Z direction) of the electrode fingers 3 and 4, is defined as he1. In this case, he1 is preferably 10 nm or more and 1200 nm or less, more preferably 50 nm or more and 700 nm or less. Furthermore, if there are deviations in the height of the first void 10 or the thickness of the electrode fingers 3 and 4, an averaged value of this sum can be used as he1.

[0114] In the first embodiment, at least one electrode finger 3 or 4 is stacked on the piezoelectric layer 2 in the excitation region C, separated by a first gap 10. Preferably, in the excitation region C, viewed from above in the Z direction, the total area of ​​the regions of the electrode fingers 3 and 4 disposed above the piezoelectric layer 2 separated by the first gap 10 is more than half the total area of ​​each of the plurality of first electrode fingers 3 and the plurality of second electrode fingers 4. That is, preferably, viewed from above in the Z direction, the total area of ​​the overlapping region of the electrode fingers 3 and 4, the excitation region C, and the first gap 10 is more than half the total area of ​​the overlapping region of the electrode fingers 3 and 4 and the excitation region C. More preferably, in the excitation region C, all of the plurality of first electrode fingers 3 and the plurality of second electrode fingers 4 are disposed on the first main surface 2a of the piezoelectric layer 2, separated by the first gap 10. That is, more preferably, viewed from above in the Z direction, the overlapping region of the electrode fingers 3 and 4 and the excitation region C completely overlaps with the first gap 10. In this way, by setting the first gap 10, it is possible to reduce unwanted waves.

[0115] Figure 17A This is a first explanatory diagram showing the resonant characteristics of the elastic wave device according to the first embodiment. Figure 17B This is a second explanatory diagram showing the resonant characteristics of the elastic wave device according to the first embodiment. Figure 17C This is a third explanatory diagram showing the resonant characteristics of the elastic wave device according to the first embodiment. More specifically, Figures 17A-17C This diagram illustrates the differences in the resonant characteristics of an elastic wave device caused by the presence or absence of the first gap 10 and the different widths of the counter electrodes 3 and 4. Figures 17A-17C In Examples 1 to 6, the presence or absence of the first gap 10 and the w / p ratio were changed as follows, and the resonance characteristics were measured. Here, w is the width of electrode fingers 3 and 4, and the center-to-center distance p between electrode fingers 3 and 4 is 4.25 μm in all Examples 1 to 6.

[0116] Example 1 (Example): There is a first gap of 10, w / p = 0.3

[0117] Example 2 (Comparative Example): No first gap 10, w / p = 0.3

[0118] Example 3 (Example): There is a first gap of 10, w / p = 0.4

[0119] Example 4 (Comparative Example): No first gap 10, w / p = 0.4

[0120] Example 5 (Example): There is a first gap of 10, w / p = 0.5

[0121] Example 6 (Comparative Example): No first gap 10, w / p = 0.5

[0122] according to Figures 17A-17C It is clear that the elastic wave devices of Examples 1, 3, and 5, which have the first gap 10, can suppress unwanted waves compared to the elastic wave devices of Examples 2, 4, and 6, which do not have the first gap 10. Therefore, it can be seen that unwanted waves can be reduced even when w / p varies in a wide range of 0.3 to 0.5.

[0123] The structure of the elastic wave device 1A is not limited to Figures 14 to 16 The structure shown is illustrated below. Modifications will be described below with reference to the accompanying drawings.

[0124] Figure 18 It is along Figure 14 The first variation of the sectional view of the EE′ line. For example... Figure 18 As shown, alternatively, in the excitation region C, a portion of the electrode fingers 3 and 4 may be stacked on the piezoelectric layer 2 through the first gap 10. That is, viewed from above in the Z direction, the first gap 10 may be located in a portion of the region of the electrode fingers 3 and 4 that overlaps with the excitation region C. In other words, viewed from above in the Z direction, the electrode fingers 3 and 4 may have a portion in the region overlapping with the excitation region C that is in contact with the first main surface 2a of the piezoelectric layer 2. Figure 18 In this example, the electrode finger 3 has an auxiliary post 11 that connects the first main surface 2a of the piezoelectric layer 2 and the electrode finger 3 in the Z direction. Here, the auxiliary post 11 is, for example, provided at the end of the electrode finger 3 in the length direction on the side not connected to the busbar 5. That is, when a first gap 10 is provided between the first electrode finger and the piezoelectric layer 2, the first gap 10 becomes a space provided in the X direction between the auxiliary post 11 and the busbar 5. In this case, unwanted waves can also be suppressed.

[0125] Figure 19 It is along Figure 14 The second variation of the sectional view of the EE′ line. For example... Figure 19 As shown, an electrode film 12 can also be further provided on the first main surface 2a of the piezoelectric layer 2 in the first gap 10. That is, the electrode fingers 3 and 4 can also be stacked on the piezoelectric layer 2 with the electrode film 12 and the first gap 10 in between.

[0126] Figure 20 It is along Figure 14 The third variation of the sectional view of the EE′ line. For example... Figure 20 As shown, a dielectric film 13 may also be further provided on the first main surface 2a of the piezoelectric layer 2 in the first gap 10. That is, the electrode fingers 3 and 4 may also be stacked on the piezoelectric layer 2 with the dielectric film 13 and the first gap 10 in between.

[0127] Figure 21 It is along Figure 14 The fourth variation of the sectional view of the FF′ line. Figure 22 It is along Figure 14 The fifth variation of the sectional view of the FF′ line. For example... Figure 21 as well as Figure 22 As shown, the elastic wave device 1A according to the first embodiment may also be provided with a mass-added film 14. The mass-added film 14 is a film provided on the second main surface 2b of the piezoelectric layer 2, and is provided at a position overlapping the electrode fingers 3 and 4 when viewed from above in the Z direction. In this case, the elastic wave device 1A is preferably configured to utilize plate waves. By adopting this configuration, unwanted waves can be further suppressed. In addition, as Figure 21 As shown, the mass-added film 14 can also be an electrode film, in which case a gap 15 can be present between it and the piezoelectric layer 2. Furthermore, as... Figure 22 As shown, the mass-added film 14 can also be a dielectric film.

[0128] The elastic wave device 1A according to the first embodiment has been described above, but the structure of the elastic wave device 1A is not limited to the structure shown above. For example, in the elastic wave device 1A, the acoustic multilayer film 42 can also be used as the energy sealing layer. Furthermore, in the elastic wave device 1A, a dielectric film 7 can also be provided between the piezoelectric layer 2 and the support substrate 8. In this case, the void 9 can also be an air gap provided between the dielectric film 7 and the piezoelectric layer 2. Furthermore, the first IDT electrode 30 is not limited to being provided on the first main surface 2a of the piezoelectric layer 2, but can also be provided on the second main surface 2b. In this case, the mass-adding film 14 can be provided on the first main surface 2a of the piezoelectric layer 2.

[0129] As described above, the elastic wave device according to the first embodiment includes: a support substrate 8; a piezoelectric layer 2 having two main surfaces in a first direction that is the thickness direction of the support substrate 8, comprising lithium niobate or lithium tantalate; an energy blocking layer disposed between the support substrate 8 and the piezoelectric layer 2 in the first direction; and a first IDT electrode 30 formed on one of the two main surfaces of the piezoelectric layer 2 (e.g., the first main surface 2a), and including a first busbar 5, a second busbar 6, a plurality of first electrode fingers 3 with their base ends connected to the first busbar 5, and a plurality of second electrode fingers 4 with their base ends connected to the second busbar 6, wherein at least one of the first IDT electrodes 30... The piezoelectric layer 2 is partially disposed in a region that overlaps with the energy sealing layer when viewed from above in the thickness direction of the support substrate 8. The thickness of the piezoelectric layer 2 is set as d, and the center-to-center distance between adjacent electrode fingers among the plurality of first electrode fingers 3 and the plurality of second electrode fingers 4 is set as p. In this case, d / p is 0.5 or less. The plurality of first electrode fingers 3 and the plurality of second electrode fingers 4 are configured to have an excitation region C that overlaps with each other when viewed from the arrangement direction of the plurality of first electrode fingers 3 and the plurality of second electrode fingers 4. In the excitation region C, a first gap 10 is provided between at least a portion of at least one of the plurality of first electrode fingers 3 and the plurality of second electrode fingers 4 and the piezoelectric layer 2.

[0130] By configuring the structure as described above, the elastic wave device according to the first embodiment can suppress the occurrence of unwanted waves compared to the case without the first gap 10. Therefore, unwanted waves can be reduced.

[0131] As a preferred embodiment, in the excitation region C, viewed from above in the thickness direction of the support substrate 8, the sum of the areas of at least a portion of the electrode fingers 3 and 4 disposed above the piezoelectric layer 2 through the first gap 10 is more than half the sum of the areas of each of the plurality of first electrode fingers 3 and each of the plurality of second electrode fingers 4. This further reduces unwanted waves.

[0132] As a further preferred embodiment, in the excitation region C, a plurality of first electrode fingers 3 and a plurality of second electrode fingers 4 are all disposed on a main surface of the piezoelectric layer 2, separated by a first gap 10. This further reduces unwanted waves.

[0133] Alternatively, a mass-added film 14 may be provided on one of the two main surfaces of the piezoelectric layer 2, which is different from one of the main surfaces (e.g., the second main surface 2b). When viewed from above in the first direction, the mass-added film 14 overlaps with at least a portion of the first electrode finger 3 or the second electrode finger 4. This further reduces unwanted waves.

[0134] As a preferred embodiment, a gap 15 is provided between at least a portion of the mass-added film 14 and the piezoelectric layer 2. This further reduces unwanted waves.

[0135] As a preferred embodiment, the energy sealing layer is the void portion 9. This allows the bulk wave of the thickness shear first mode and other elastic waves to be contained within the piezoelectric layer 2.

[0136] As a preferred embodiment, the energy-sealing layer is an acoustic reflection layer (e.g., an acoustic multilayer film 42) stacked with a low acoustic impedance layer and a high acoustic impedance layer, wherein the low acoustic impedance layer has a lower acoustic impedance than the piezoelectric layer 2, and the high acoustic impedance layer has a higher acoustic impedance than the piezoelectric layer 2. This allows for the containment of thickness-shear first-order mode bulk waves and other elastic waves within the piezoelectric layer 2.

[0137] As a preferred embodiment, the piezoelectric layer 2 is formed by the Euler angle of lithium niobate or lithium tantalate. θ and ψ are within the range of equations (1), (2), or (3) below. In this case, the relative bandwidth can be sufficiently widened.

[0138] (0°±10°, 0°~20°, any ψ) …Equation (1)

[0139] (0°±10°, 20°~80°, 0°~60°(1-(θ-50) 2 / 900) 1 / 2 () or (0°±10°, 20°~80°, [180°-60°(1-(θ-50))) 2 / 900) 1 / 2 [~180°) …Equation (2)

[0140] (0°±10°,[180°-30°(1-(ψ-90) 2 / 8100) 1 / 2 ~180°, any ψ)

[0141] …Formula (3)

[0142] As a preferred embodiment, the elastic wave device is configured to utilize a volume wave with a thickness shear mode. This increases the coupling coefficient and provides an elastic wave device with excellent resonance characteristics.

[0143] Preferably, d / p is 0.24 or less. This allows for miniaturization of the elastic wave device 1 and improves the Q value.

[0144] As a preferred embodiment, when the metallization ratio of the multiple electrode fingers 3, 4 relative to the excitation region C is set to MR, MR ≤ 1.75(d / p) + 0.075 is satisfied. In this case, the relative bandwidth can be reliably kept below 17%.

[0145] As a preferred embodiment, the elastic wave device is configured to utilize plate waves. This provides an elastic wave device with excellent resonance characteristics.

[0146] (Second Implementation)

[0147] Figure 23 This is a top view showing an embodiment of the elastic wave device according to the second embodiment. The elastic wave device 1B according to the second embodiment differs from that of the first embodiment in that it also includes a second IDT electrode 30A. In the second embodiment, the same reference numerals are used for structures identical to those in the first embodiment, and descriptions are omitted.

[0148] like Figure 23 As shown, the elastic wave device 1B according to the second embodiment includes a first resonator having a first IDT electrode 30 and a second resonator having a second IDT electrode 30A. The first resonator and the second resonator may also constitute the same filter. In this case, the filter can be, for example, a trapezoidal filter.

[0149] The second IDT electrode 30A is an IDT electrode having a third busbar 5A, a fourth busbar 6A, a plurality of third electrode fingers 3A connected to the third busbar 5A at their base ends, and a plurality of fourth electrode fingers 4A connected to the fourth busbar 6A at their base ends. The second IDT electrode 30A is disposed on the first main surface 2a of the piezoelectric layer 2. Here, the second IDT electrode 30A has an excitation region CA. The excitation region CA is the region where the electrode fingers 3A and 4A overlap when viewed in the X direction orthogonal to the length direction (Y direction) of the electrode fingers 3A and 4A.

[0150] Figure 24 It is along Figure 23 An example of a cross-sectional view of the GG' line. Figure 25 It is along Figure 23 An example of a cross-sectional view of the HH′ line. For example... Figure 25 As shown, a second gap 10A is provided between electrode fingers 3A and 4A and the piezoelectric layer 2. Here, the height of the second gap 10A, that is, the length of the second gap 10A in the Z direction, is defined as hv2. In this case, hv2 is preferably 1 nm or more and 100 nm or less, more preferably 10 nm or more and 20 nm or less. In addition, if the height of the second gap 10A has a deviation, an average value of that height can be used as hv2.

[0151] Furthermore, hv2 is preferred with Figure 24The height hv1 shown is different for the first gap 10. By adjusting hv2, the elastic wave device 1B according to the second embodiment can adjust the relative bandwidth of the second resonator without adding a capacitor, thus making it easy to adjust the relative bandwidth of the second resonator while suppressing the enlargement of the elastic wave device 1B.

[0152] The second gap 10A is the space between the third electrode finger 3A or the fourth electrode finger 4A and the first main surface 2a of the piezoelectric layer 2. Figure 25 In the example, the second gap 10A opens upwards on the side of the electrode fingers 3A and 4A in both the X and Y directions that are not connected to the busbars 5A and 6A. Here, the sum of the heights of the electrode fingers 3A and 4A, i.e., the height of the second gap 10A and the thickness (length in the Z direction) of the electrode fingers 3A and 4A, is defined as he2. In this case, he2 is preferably 10 nm or more and 1200 nm or less, more preferably 50 nm or more and 700 nm or less. Furthermore, if there are deviations in the height of the second gap 10A or the thickness of the electrode fingers 3A and 4A, the average of their sums can be used as he2.

[0153] In the second embodiment, at least one electrode finger 3A, 4A is stacked on the piezoelectric layer 2 in the excitation region CA, separated by a second gap 10A. Preferably, in the excitation region CA, viewed from above in the Z direction, the total area of ​​the regions of the electrode fingers 3A, 4A disposed above the piezoelectric layer 2 separated by the second gap 10A is more than half the total area of ​​each of the plurality of third electrode fingers 3A and the plurality of fourth electrode fingers 4A. That is, preferably, viewed from above in the Z direction, the total area of ​​the overlapping regions of the electrode fingers 3A, 4A, the excitation region C, and the second gap 10A is more than half the total area of ​​the overlapping regions of the electrode fingers 3A, 4A, and the excitation region C. More preferably, in the excitation region C, all of the plurality of third electrode fingers 3A and the plurality of fourth electrode fingers 3A are disposed on the first main surface 2a of the piezoelectric layer 2, separated by the second gap 10A. That is, more preferably, when viewed from above in the Z direction, the area where the electrode fingers 3A, 4A and the excitation region CA overlap completely overlaps with the second gap 10A.

[0154] Figure 26 This is a first explanatory diagram showing the resonant characteristics of the elastic wave device according to the second embodiment. Figure 27 This is a second explanatory diagram showing the resonant characteristics of the elastic wave device according to the second embodiment. More specifically, Figure 26 This is a diagram showing the resonance characteristics of different elastic wave devices 1B with hv2. Figure 27 This is a diagram showing the relationship between the relative bandwidth and the anti-resonance frequency of the elastic wave device according to the second embodiment. Additionally, [the following is obtained] Figure 26The design parameters for Examples 7 to 9 of the elastic wave device 1B, which show the resonant characteristics, are as follows.

[0155] In Example 7, hv2 is 2 nm. Furthermore, in Example 7, the piezoelectric layer 2 is LiNbO3 with Euler angles of (0°, 37.5°, 0°) and a thickness of 390 nm.

[0156] In Example 8, hv2 is 6 nm. Furthermore, the piezoelectric layer 2 in Example 8 is LiNbO3 with Euler angles of (0°, 37.5°, 0°) and a thickness of 390 nm.

[0157] In Example 9, hv2 is 10 nm. Furthermore, the piezoelectric layer 2 in Example 9 is LiNbO3 with Euler angles of (0°, 37.5°, 0°) and a thickness of 390 nm.

[0158] according to Figure 26 as well as Figure 27 It is clear that by changing hv2, only the anti-resonance frequency of the second resonator can be shifted, thus allowing adjustment of the relative bandwidth of the second resonator. Therefore, the elastic wave device 1B according to the second embodiment can adjust the relative bandwidth without adding a capacitor, thereby easily adjusting the relative bandwidth of the second resonator while suppressing the enlargement of the elastic wave device 1B.

[0159] As described above, the elastic wave device 1B according to the second embodiment further includes: a second IDT electrode 30A formed on a main surface, and including a third bus bar 5A, a fourth bus bar 6A facing each other, a plurality of third electrode fingers 3A connected to the base end of the third bus bar 5A, and a plurality of fourth electrode fingers 4A connected to the base end of the fourth bus bar 6A. The plurality of third electrode fingers 3A and the plurality of fourth electrode fingers 4A are configured to have an excitation region C that overlaps when viewed from the arrangement direction of the plurality of third electrode fingers 3A and the plurality of fourth electrode fingers 4A. In the excitation region C, a gap is provided between at least a portion of at least one of the plurality of third electrode fingers 3A and the plurality of fourth electrode fingers 4A and the piezoelectric layer 2. The height hv1 of the first gap 10, which is a gap in the first IDT electrode 30, and the height hv2 of the second gap 10A, which is a gap in the second IDT electrode 30A, are different. Therefore, by adjusting the height hv2 of the second gap 10A, the relative bandwidth can be adjusted without adding a capacitor, thus enabling easy adjustment of the relative bandwidth while suppressing the enlargement of the elastic wave device 1B.

[0160] Furthermore, the first resonator equipped with the first IDT electrode 30 and the second resonator equipped with the second IDT electrode 30A can also constitute the same filter. Even in this case, by adjusting the height hv2 of the second gap 10A, the relative bandwidth can be adjusted without adding a capacitor, thus enabling easy adjustment of the relative bandwidth while suppressing the enlargement of the elastic wave device 1B.

[0161] Furthermore, the above-described embodiments are intended to facilitate understanding of this disclosure and are not intended to limit its interpretation. This disclosure can be modified / improved without departing from its spirit, and it also includes equivalents.

[0162] Explanation of reference numerals in the attached figures

[0163] 1, 1A, 1B, 41, 101, 301: Elastic wave devices;

[0164] 2: Piezoelectric layer;

[0165] 2a: First main face;

[0166] 2b: Second main face;

[0167] 3: The first electrode refers to;

[0168] 4: The second electrode indicates;

[0169] 5: First busbar;

[0170] 6: Second busbar;

[0171] 3A: The third electrode refers to;

[0172] 4A: The fourth electrode;

[0173] 5A: Busbar 3;

[0174] 6A: Bus 4;

[0175] 7: Dielectric film;

[0176] 8: Support base plate;

[0177] 7a, 8a: Openings;

[0178] 9: Hollow section;

[0179] 10: First gap;

[0180] 10A: Second gap;

[0181] 11: Auxiliary column;

[0182] 12: Electrode film;

[0183] 13: Dielectric film;

[0184] 14: Quality-added film;

[0185] 15: Gap;

[0186] 30: First IDT electrode;

[0187] 30A: Second IDT electrode;

[0188] 42: Multilayer acoustic membrane;

[0189] 42a: Low acoustic impedance layer;

[0190] 42b: High acoustic impedance layer;

[0191] 42c: Low acoustic impedance layer;

[0192] 42d: High acoustic impedance layer;

[0193] 42e: Low acoustic impedance layer;

[0194] 201: Piezoelectric layer;

[0195] 201a: 1st main surface;

[0196] 201b: Second main face;

[0197] 310, 311: Reflectors;

[0198] 451: Region 1;

[0199] 452: Region 2;

[0200] C, CA: Excitation region;

[0201] VP1: Imaginary plane.

Claims

1. An elastic wave device, comprising: support base plate; The piezoelectric layer has two main surfaces in a first direction, which serves as the thickness direction of the supporting substrate, and comprises lithium niobate or lithium tantalate. An energy-sealing layer is disposed in a first direction between the support substrate and the piezoelectric layer; and The first IDT electrode is formed on one of the two main surfaces of the piezoelectric layer, and includes a first busbar, a second busbar, a plurality of first electrode fingers whose base ends are connected to the first busbar, and a plurality of second electrode fingers whose base ends are connected to the second busbar. At least a portion of the first IDT electrode is disposed in a region that at least partially overlaps with the energy containment layer when viewed from above in the thickness direction of the support substrate. Let the thickness of the piezoelectric layer be d, and let the center-to-center distance between adjacent electrode fingers among the plurality of first electrode fingers and the plurality of second electrode fingers be p. In this case, d / p is less than 0.

5. The plurality of first electrode fingers and the plurality of second electrode fingers are configured to have overlapping intersecting regions when viewed from the arrangement direction of the plurality of first electrode fingers and the plurality of second electrode fingers. In the intersection region, a first gap is provided between at least a portion of at least one of the plurality of first electrode fingers and the plurality of second electrode fingers and the piezoelectric layer.

2. The elastic wave device according to claim 1, wherein, In the intersection region, viewed from above in the thickness direction of the support substrate, the sum of the areas of at least a portion of the electrode fingers disposed above the piezoelectric layer through the first gap is more than half the sum of the areas of each of the plurality of first electrode fingers and the areas of each of the plurality of second electrode fingers.

3. The elastic wave device according to claim 2, wherein, In the intersection region, the plurality of first electrode fingers and the plurality of second electrode fingers are all disposed on the main surface of the piezoelectric layer through the first gap.

4. The elastic wave device according to any one of claims 1 to 3, wherein, It also includes: a second IDT electrode formed on the main surface, and comprising mutually opposing third and fourth busbars, a plurality of third electrode fingers with base ends connected to the third busbars, and a plurality of fourth electrode fingers with base ends connected to the fourth busbars. The plurality of third electrode fingers and the plurality of fourth electrode fingers are configured to have overlapping intersecting regions when viewed from the arrangement direction of the plurality of third electrode fingers and the plurality of fourth electrode fingers. In the intersection region, a second gap is provided between at least a portion of at least one of the plurality of third electrode fingers and the plurality of fourth electrode fingers and the piezoelectric layer. The height of the first gap is different from the height of the second gap.

5. The elastic wave device according to claim 4, wherein, A first resonator having the first IDT electrode and a second resonator having the second IDT electrode constitute the same filter.

6. The elastic wave device according to any one of claims 1 to 5, wherein, A mass-added film is further provided on the other main surface of the piezoelectric layer, which is different from one of the main surfaces. Viewed from above in the first direction, the mass-added film overlaps with at least a portion of the first electrode finger or the second electrode finger.

7. The elastic wave device according to claim 6, wherein, A gap is provided between at least a portion of the mass-added film and the piezoelectric layer.

8. The elastic wave device according to any one of claims 1 to 7, wherein, The energy sealing layer is hollow.

9. The elastic wave device according to any one of claims 1 to 7, wherein, The energy sealing layer is an acoustic reflection layer consisting of a low acoustic impedance layer and a high acoustic impedance layer. The low acoustic impedance layer has a lower acoustic impedance than the piezoelectric layer, and the high acoustic impedance layer has a higher acoustic impedance than the piezoelectric layer.

10. The elastic wave device according to any one of claims 1 to 9, wherein, Euler angles of lithium niobate or lithium tantalate constituting the piezoelectric layer Within the range of the following equations (1), (2), or (3), (0°±10°, 0°~20°, any ψ)…Equation (1) (0°±10°, 20°~80°, 0°~60°(1-(O-50) 2 / 900) 1 / 2 () or (0°±10°, 20°~80°, [180°-60°(1-(θ-50))) 2 / 900) 1 / 2 [~180°)…Equation (2) (0°±10°,[180°-30°(1-(ψ-90) 2 / 8100) 1 / 2 ]~180°, any ψ)…Equation (3).

11. The elastic wave device according to any one of claims 1 to 10, wherein, It is configured as a volume wave that can utilize the thickness shear mode.

12. The elastic wave device according to any one of claims 1 to 11, wherein, The d / p ratio is below 0.

24.

13. The elastic wave device according to any one of claims 1 to 12, wherein, When the metallization ratio of the plurality of first electrode fingers or the plurality of second electrode fingers relative to the cross region is set as MR, MR ≤ 1.75(d / p) + 0.075 is satisfied.

14. The elastic wave device according to any one of claims 1 to 9, wherein, It is configured to utilize plate waves.

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